Cri­te­ria for Fin­ding a Donor

HLA cha­rac­te­ristics & gene­tic twins

To mini­mi­ze the risk of rejec­tion, it is essen­ti­al to find a donor who has the same tis­sue cha­rac­te­ristics as the pati­ent – a gene­tic twin. The­se cha­rac­te­ristics, cal­led human leu­ko­cy­te anti­gens (HLA), are tiny struc­tures on the sur­face of the cells in the body. Based on their shape, the body distin­gu­is­hes bet­ween tho­se that belong in the body and tho­se that don’t.
The genes (blue­prints) of the five most important HLA cha­rac­te­ristics – A, B, C, DRB1 and DQB1 – are loca­ted on one sin­gle chro­mo­so­me and are the­r­e­fo­re inhe­ri­ted joint­ly as a “haplo­ty­pe.” Every per­son inhe­rits one HLA haplo­ty­pe from each of their par­ents. The­re are over a hundred vari­ants of each HLA cha­rac­te­ristic, and the pos­si­ble com­bi­na­ti­ons reach the tril­li­on mark. Hence, the likeli­hood of fin­ding two peo­p­le with iden­ti­cal tis­sue cha­rac­te­ristics is very low and the search for a sui­ta­ble unre­la­ted donor both com­plex and elaborate.

Is it kept in the family?

The first step is to check whe­ther the­re is a gene­tic twin in the fami­ly. The likeli­hood of fin­ding a sui­ta­ble donor among siblings is 25%. Among other fami­ly mem­bers, the chan­ces are gene­ral­ly much lower. As fami­lies in Ger­ma­ny tend to be small, rela­ti­ves are found to be sui­ta­ble donors for appro­xi­m­ate­ly one third of pati­ents only, on average.

Fin­ding an unre­la­ted donor

For the remai­ning two thirds, an unre­la­ted donor must be found. The atten­ding doc­tor the­r­e­fo­re cont­acts the rele­vant search cen­ter and they agree on the search cri­te­ria. The cen­ter then for­wards all the neces­sa­ry infor­ma­ti­on and docu­ments to the ZKRD. The ZKRD sear­ches the natio­nal and inter­na­tio­nal donor data­ba­ses to obtain a list of poten­ti­al, sui­ta­ble donors. The search cen­ter then sel­ects an appro­pria­te donor for the respec­ti­ve pati­ent accor­ding to defi­ned tech­ni­cal criteria.